24 crew members of Ukrainian ships were arrested by the Russian Coast Guard in November 2018 for violating Russian maritime borders in the Kerch Strait.
Recurring pro-Kremlin disinformation about the Kerch incident.
On the 25th of November 2018, border patrol boats belonging to Russia’s FSB security service seized two small Ukrainian armoured artillery vessels and a tug boat and their crews after shooting at them, wounding several Ukrainian servicemen and arresting 24 members.
Russia stated they were in Russian waters. However, according to the bilateral agreement between Ukraine and Russia, the Kerch Strait and the Sea of Azov are the internal waters of both Russia and Ukraine.
The agreement gives both parties the power to inspect suspicious vessels. Furthermore, both the 2003 bilateral agreement and UN Convention on the Law of the Sea provide for freedom of navigation.
See here for a similar case.